Islamist gunmen destroyed several tombs in Timbuktu on Sunday, residents said, days after the United Nations authorised African states to ready a force to take on al Qaeda-linked groups in Mali's northern desert zones.

"Since 0800 (GMT) this morning, the Islamists have been destroying tombs again," Youssouf Toure, a resident of the ancient trading town, told Reuters by telephone. "(They are) targeting new ones and the ones they destroyed several months ago," he added. Residents said the attacks on traditional Sufi Islamic shrines were being carried out by about 15 heavily-armed fighters, some weilding pick axes. At least two previously untouched tombs in Timbuktu, a UNESCO world heritage site, were destroyed on Sunday, residents said.

A mix of Islamists with links to al Qaeda have occupied Mali's north since April. Since then, they have destroyed much of the region's religious heritage and carried out a string of amputations in the name of imposing strict Islamic law on a population that has practised a more moderate form of Islam for centuries. Sanda Ould Boumana, spokesman for Ansar Dine, the group officially in control of Timbuktu, declined to comment on the latest attacks on tombs. But one resident said an Islamist fighter who took part in the tomb-smashing said they were being carried out to prove to the world that they would not be swayed by the threat of foreign military intervention.

The UN Security Council last week authorised the deployment of an Africa-led force to retrain Mali's defeated army and ultimately support an offensive to retake territory currently controlled by Islamists. No military offensive is expected before late next year. But Timbuktu residents said that Islamists there had been on edge since the U.N. approved the mission. "They are destroying anything that crosses their path," said one resident, who gave his name only as Maiga. Some 400,000 people have fled their homes in Mali this year. The rebellion was launched by separatist Tuareg rebels but has since been hijacked by better armed and funded Islamists operating alongside al Qaeda fighters in the Sahara.